RHSA-2016:0304 - Security Advisory

Topic

Updated openssl packages that fix multiple security issues are now
available for Red Hat Enterprise Linux 5.6 and 5.9 Long Life.

Red Hat Product Security has rated this update as having Important security
impact. Common Vulnerability Scoring System (CVSS) base scores, which give
detailed severity ratings, are available for each vulnerability from the
CVE links in the References section.

Description

OpenSSL is a toolkit that implements the Secure Sockets Layer (SSL v2/v3)
and Transport Layer Security (TLS v1) protocols, as well as a
full-strength, general purpose cryptography library.

A padding oracle flaw was found in the Secure Sockets Layer version 2.0
(SSLv2) protocol. An attacker can potentially use this flaw to decrypt
RSA-encrypted cipher text from a connection using a newer SSL/TLS protocol
version, allowing them to decrypt such connections. This cross-protocol
attack is publicly referred to as DROWN. (CVE-2016-0800)

Note: This issue was addressed by disabling the SSLv2 protocol by default
when using the 'SSLv23' connection methods, and removing support for weak
SSLv2 cipher suites. It is possible to re-enable the SSLv2 protocol in the
'SSLv23' connection methods by default by setting the OPENSSL_ENABLE_SSL2
environment variable before starting an application that needs to have
SSLv2 enabled. For more information, refer to the knowledge base article
linked to in the References section.

It was discovered that the SSLv2 servers using OpenSSL accepted SSLv2
connection handshakes that indicated non-zero clear key length for
non-export cipher suites. An attacker could use this flaw to decrypt
recorded SSLv2 sessions with the server by using it as a decryption
oracle.(CVE-2016-0703)

It was discovered that the SSLv2 protocol implementation in OpenSSL did
not properly implement the Bleichenbacher protection for export cipher
suites. An attacker could use a SSLv2 server using OpenSSL as a
Bleichenbacher oracle. (CVE-2016-0704)

Note: The CVE-2016-0703 and CVE-2016-0704 issues could allow for more
efficient exploitation of the CVE-2016-0800 issue via the DROWN attack.

A denial of service flaw was found in the way OpenSSL handled SSLv2
handshake messages. A remote attacker could use this flaw to cause a
TLS/SSL server using OpenSSL to exit on a failed assertion if it had both
the SSLv2 protocol and EXPORT-grade cipher suites enabled. (CVE-2015-0293)

A flaw was found in the way malicious SSLv2 clients could negotiate SSLv2
ciphers that have been disabled on the server. This could result in weak
SSLv2 ciphers being used for SSLv2 connections, making them vulnerable to
man-in-the-middle attacks. (CVE-2015-3197)

Red Hat would like to thank the OpenSSL project for reporting these issues.
Upstream acknowledges Nimrod Aviram and Sebastian Schinzel as the original
reporters of CVE-2016-0800 and CVE-2015-3197; David Adrian (University of
Michigan) and J. Alex Halderman (University of Michigan) as the original
reporters of CVE-2016-0703 and CVE-2016-0704; and Sean Burford (Google) and
Emilia Kasper (OpenSSL development team) as the original reporters of
CVE-2015-0293.

All openssl users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. For the update to take
effect, all services linked to the OpenSSL library must be restarted, or
the system rebooted.

Solution

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux Server - AUS 5.9 x86_64
• Red Hat Enterprise Linux Server - AUS 5.9 ia64
• Red Hat Enterprise Linux Server - AUS 5.9 i386
• Red Hat Enterprise Linux Server - AUS 5.6 x86_64
• Red Hat Enterprise Linux Server - AUS 5.6 ia64
• Red Hat Enterprise Linux Server - AUS 5.6 i386

Fixes

• BZ - 1202404 - CVE-2015-0293 openssl: assertion failure in SSLv2 servers
• BZ - 1301846 - CVE-2015-3197 OpenSSL: SSLv2 doesn't block disabled ciphers
• BZ - 1310593 - CVE-2016-0800 SSL/TLS: Cross-protocol attack on TLS using SSLv2 (DROWN)
• BZ - 1310811 - CVE-2016-0703 openssl: Divide-and-conquer session key recovery in SSLv2
• BZ - 1310814 - CVE-2016-0704 openssl: SSLv2 Bleichenbacher protection overwrites wrong bytes for export ciphers

CVEs

• CVE-2015-0293
• CVE-2016-0703
• CVE-2016-0704
• CVE-2016-0800
• CVE-2015-3197

References

• https://access.redhat.com/security/updates/classification/#important
• https://access.redhat.com/articles/2176731
• https://drownattack.com/
• https://openssl.org/news/secadv/20160128.txt
• https://openssl.org/news/secadv/20160301.txt